Monday, March 5, 2018

Thoracic Oncology

Thoracic Oncology
 
PET Imaging of Esophageal Cancer
(click here to watch video)


Course Video Transcript
Good morning.
 
My name is Ka Kit Wong.
 
I'm a Nuclear Medicine Physician at the University of Michigan.
 
We're going to be going through PET/CT imaging of esophageal cancer.
 
The objectives of the talk are to appreciate the diagnosis,
 
staging, work up, and management of esophageal cancer.
 
To describe typical FDG PET CT findings of the primary tumor, regional,
 
and distant metastases.
 
To review indications and test performance of FDG PET CT for staging and
 
restaging compared to standard anatomic imaging, CT and endoscopic ultrasound.
 
A question, which of the following statements regarding
 
FDG PET/CT imaging of esophageal cancer is true?
 
A) PET/CT has a high great than 90% sensitive for
 
detecting T1 and T2 primary esophageal cancers.
 
B) The introduction of PET/CT for preoperative staging has made CT and
 
endoscopic ultrasound obsolete.
 
C) PET/CT has superior specificity than CT and
 
endoscopic ultrasound for staging of regional nodal metastases.
 
And D) PET/CT performs poorly for detecting distant metastases to bone.
 
Esophageal cancer is a rare tumor.
 
10% of all gastrointestinal malignancies with a poor 5-year
 
survival between 14 to 20%.
 
Squamous cell cancer accounts for 50-70% and adenocarcinoma 30-50% of all cancers.
 
Squamous cell cancer affects the middle and distal thirds.
 
And alcohol and smoking are risk factors.
 
Adenocarcinoma is becoming more common in a fixed distal part and
 
this is associated with Barrett's esophagus.
 
Only 15% of esophageal cancers are proximal third tumors.
 
The esophagus does not have serosa therefore infiltration into
 
the mediastinum occurs early.
 
The esophagus is lymphatic- and vascular-rich; therefore,
 
it is prone to early nodal and distant metastatic disease.
 
Distant sites are the liver, adrenal, lung, and
 
bone, with spread at diagnosis of 20 to 30% of cases.
 
Early stage disease is often asymptomatic.
 
However, late stage disease presents with dysphagia due to obstruction.
 
Staging of esophageal cancer follows the American Joint Committee on
 
Cancer's Seventh Edition TNM staging system.
 
The seventh edition defines regional nodes to the level of the celiac axis.
 
The number of disease nodes may be more important for
 
prognosis rather than the actual sites of these nodes.
 
This is example of the T-staging system.
 
A TX score is when the primary tumor cannot be assessed.
 
Very early, small tumors are T1.
 
T1b, invading the submucosa.
 
And large, invasive tumors are T4.
 
Being T4a, resectable, or T4b, unresectable.
 
In terms of an N stage, when you have N0,
 
there's no evidence of regional lymph node metastases.
 
And then you can have N1, N2, or N3 disease,
 
depending on the number of lymph nodes.
 
The individual T, N, and M scores are combined to reach a stage
 
one to four with four being the presence of distenmastate disease.
 
54 to 69% of patients are eligible for surgery.
 
The main survival after surgery however is only 13%-19%.
 
Neoadjuvant chemotherapy and
 
external beam radiation therapy prior to operation is gaining acceptance.
 
Conventional work-up is fluoroscopy, CT, MRI, endoscopic ultrasound.
 
PET/CT, positron emission tomography with hybrid CT Using
 
18F-fluorodeoxyglucose is a relatively new imaging modality.
 
Adenocarcinoma and
 
squamous cell carcinomas have overall similar metabolic signatures.
 
Adenocarcinomas mucinous types near the gastro-esophageal
 
junction may have slightly less FDG uptake than squamous cell cancers.
 
The majority though not all literature support the intensity of FDG uptake is
 
correlated to survival.
 
FDG uptake is a prognostic indicator.
 
Primary tumor SUVs of less than 3.0 have better survival.
 
Prognostic indicators such as the length of tumor, number of N1 positive
 
lymph nodes and distant FDG-avid sites also predict a lower survival.
 
Indications for PET/CT include a strategy to detect distant metastases at diagnosis.
 
Improving the specificity of lymph node staging, combining PET/CT and endoscopic
 
ultrasound guided biopsy as a preoperative workup for the highest nodal yield.
 
PET/CT Performance.
 
For locoregional staging,
 
PET/CT has a sensitivity of 51% and a specificity of 94%.
 
For distance staging, it has a sensitivity of 67% and a specificity of 84%.
 
For the primary tumor, PET CT has overall sensitivity of 80% for
 
primary esophageal cancer.
 
The sensitivity is close to a 100% for large tumors T3 and
 
T4 but the sensitivity is only 43% for smaller T1 tumors.
 
PET/CT cannot detect inside you or T1a tumors.
 
PET/CT cannot determine the T stage of an esophageal cancer.
 
This is a PET/CT scan, which shows intense FDG outtake in the distill esophagus.
 
The fusion FDG PET/CT images, show that it's localized to the distill esophagus.
 
This image shows the PET on the top and the fusion PET/CT on the bottom.
 
There are FDG avid long nodules compatible with nodal metastatic disease.
 
This is a different case.
 
There is intensive FDG uptake which localizes to the upper
 
cervical esophagus with circumferential mucosal thickening.
 
This is compatible with a cervical esophageal cancer.
 
This PET image shows EDG outtake in prevascular lymph node.
 
This is compatible with nodal metastatic disease.
 
This actual image shows FDG uptake in a lung nodule in the right middle lobe.
 
This is compatible with lung metastasis.
 
Some pitfalls of FDG PET/CT are that mild esophageal uptake
 
with an SUV max of less than four may actually related to esophagitis or
 
lower esophageal sphincter activity.
 
Hiatal hernias, benign stricture after dilatations, post-biopsy and
 
esophageal leiomyomas can have mild FDG uptake.
 
These are sources of false-positive results.
 
Small intracapsular nodal metastases have a high false-negative rate.
 
Intense uptake in the primary tumor may obscure subtle abnormal adjacent nodes.
 
Synchronous primary neoplasms are found in 5.5 to 8% of patients for
 
esophageal cancer on PET scanning.
 
PET/CT compared to CT and endoscopic ultrasound combination for
 
nodal staging shows that PET although being less sensitive,
 
22%, has a very high specificity of 91% compared to CT/EUS,
 
83% sensitivity but only 45% specificity.
 
Therefore, the combination of PET CT and
 
CT/EUS would have the highest diagnostic accuracy.
 
PET/CT versus CT for distant MI disease.
 
The PET scan has a sensitivity of 69% and a specificity of 93%.
 
Whereas the CT has only a sensitivity of 46% and the lowest specificity of 74%.
 
In PET/CT adverse to CT for M1 bone disease.
 
The PET has a sensitivity of 92% and a specificity of 94%,
 
which is superior to CT of 77% and specificity of 84%.
 
This is a case showing FDG avid bone metastasis and
 
the arrow is localizing lumber's fine bone metastasis in this
 
patient with esophageal cancer.
 
These axial images show FDG [INAUDIBLE] rib metastases.
 
This image in the same patient show FDG avid bone metastases
 
to the right pubic synthesis and the left femoral head.
 
The impact of PET/CT on patient management is that it will change
 
staging in 14% of patients.
 
PET will find distant metastatic diseases in additional 5 to 8%
 
of patients after conventional imaging workup.
 
PET is insensitive for locoregional disease and
 
does not replace CT/endoscopic ultra sound for detection of neural disease.
 
PET is more specific than CT/endoscopic ultra sound for regional and
 
distant disease.
 
Using PET/CT for detection of recurrences two-thirds
 
of patients relapse within one to two years after their diagnosis.
 
For re-staging PET/CT has been shown to have a sensitivity of 94% and
 
a specificity of 82% for detection of recurrent metastatic disease.
 
PET is not really better than the conventional modality CT and MRI.
 
PERCIST is an acronym for therapeutic response criteria, based on PET imaging.
 
RECIST is an acronym for therapeutic response criteria based on CT,
 
which looks at changes in size of tumor sites.
 
By using PERCIST criteria, which is based on the metabolic signature,
 
which is the FDG uptaking tumor and the changes after treatment.
 
Treatment response, monitoring is better than using the older RECIST criteria.
 
Responders versus non-responders on early response PET/CT is
 
associated with better survival in some studies with a threshold
 
of SUV reduction between 30 to 80% being advocated.
 
PET cannot exclude minimal residual disease as there is
 
cases of significant recurrence even after a SUV decline.
 
So going back to the multi-choice question from earlier, which of the following
 
statements regarding FDG PET/CT imaging of esophageal cancer is true?
 
The answer is, C, the PET/CT has superior specificity
 
than CT/endoscopic Ultrasound for staging of regional nodal metastases.
 
Therefore, the combination of PET/CT with CT and
 
endoscopic ultrasound together will have the highest diagnostic accuracy.
 
Some take home points.
 
Esophageal cancer is a biologically aggressive,
 
metabolically active malignancy.
 
FDG PET/CT is a useful imaging modality for staging and restaging
 
of esophageal cancer, prognostication, and assessing treatment response.
 
FDG PET/CT has good specificity for loco-regional nodal metastases.
 
FDG PET/CT is a whole-body technique with good accuracy for
 
distant metastatic disease.
 
This is a bibliography of relevent articles on PET/CT for esophagus cancer.
 
So PET/CT is a relatively new, very powerful imaging methodology for
 
the diagnosis and staging of a wide range of cancers, including esophageal cancer.
 
I'd like to thank you for your participation in this educational lecture,
 
hope that its been helpful.
 
Thank you.
 
 

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